The present invention relates to an improved machine for the continuous decorating of the exterior side walls of cylindrical cans.
More particularly, this invention relates to a machine for decorating the cylindrical body of a two-piece can with color-on-color or overlay printing.
One traditional process of decorating cans has been used with the three-piece cans in which the can consists of a bottom disk, a cylindrical side wall and a top disk, all of which are joined together. The side wall or "body" of the can is printed or otherwise decorated when it is in the form of a flat linear sheet prior to fabrication into a cylinder. A two-piece can is usually drawn from aluminum or steel or other ductile metal into a cylinder form which is integral with a bottom closure portion. The top cap is applied in a subsequent operation. The side wall of the conventional two-piece can is never in a flat sheet form suitable for printing upon. Canning plants frequently prefer to decorate directly upon the outer surface of a cylindrical body of a two-piece can after it is formed into cylindrical form, but prior to subsequent filling of the canned material, rather than use the decoration of a separate paper label which may be pasted to the two-piece can.
Various types of rotary printing machines, generally using solvent inks and separate curing ovens, are known for printing directly upon cans. However, the printing machines and required curing ovens are relatively expensive in capital cost, they are generally costly to operate in terms of energy usage, and they occupy a relatively large amount of factory floor space. Also, for those can decorations that require a base coat, separate base coaters and curing ovens are required. In addition, the conventional machines are not adapted for the highest quality of multi-color printing at high speeds because they are limited to laying down colors in a side-to-side relationship on the side walls of the two-piece cans.
It is known from the John Jackson U.S. Pat. No. 3,645,201 to provide a multi-color printing machine for cylindrical objects in which the rotating mandrels are indexed to printing and drying stations. In the Jackson machine the index table is horizontal and the mandrels are mounted horizontally; the ink is a volatile printing ink which uses hot air drying between color laydowns; the index table is rotated intermediately by an indexing mechanism and the mandrels are rotated by bevel gears. The use of volatile inks, the use of one station only for drying these inks, and the general machine configuration limits the speed of operation of the Jackson machine and thus affects its economic feasibility for two-piece can decorating.
In the machine described in Gladfelter U.S. Pat. No. 2,326,850 a metal can printing machine includes a can-support turret and a plurality of printing assemblies each including a transfer cylinder. The printing assemblies are driven by a large gear but the cans are not held on driven rotating mandrels. That machine has not been found to be commercially acceptable for present high-speed can manufacturing.